Metric Fasteners
This vehicle is dimensioned in the metric system. Most metric fasteners
are very close in diameter to well known fasteners in the English, inch system.
Replace fasteners with those of the same nominal diameter, thread pitch,
and strength.
A number marking identifies the OE metric fasteners except cross-recess
head screws. The number also indicates the strength of the fastener material.
A Posidrive® or Type 1A cross-recess identifies a metric cross-recess
screw. For best results, use a Type 1A cross-recess screwdriver,
or equivalent, in Posidrive® recess head screws.
GM Engineering Standards and North American Industries have adopted
a portion of the ISO-defined standard metric fastener sizes. The purpose was
to reduce the number of fastener sizes used while retaining the best
thread qualities in each thread size. For example, the metric M6.0 X 1
screw, with nearly the same diameter and 25.4 threads per inch
replaced the English 1/4-20 and 1/4-28 screws. The thread
pitch is midway between the English coarse and fine thread pitches.
Fastener Strength Identification